title: Regioselectivity of enzymatic and photochemical single electron transfer promoted carbon-carbon bond fragmentation reactions of tetrameric lignin model compounds.
abstract: New types of tetrameric lignin model compounds, which contain the common β-O-4 and β-1 structural subunits found in natural lignins, have been prepared and carbon-carbon bond fragmentation reactions of their cation radicals, formed by photochemical (9,10-dicyanoanthracene) and enzymatic (lignin peroxidase) SET-promoted methods, have been explored. The results show that cation radical intermediates generated from the tetrameric model compounds undergo highly regioselective C-C bond cleavage in their β-1 subunits. The outcomes of these processes suggest that, independent of positive charge and odd-electron distributions, cation radicals of lignins formed by SET to excited states of sensitizers or heme-iron centers in enzymes degrade selectively through bond cleavage reactions in β-1 vs β-O-4 moieties. In addition, the findings made in the enzymatic studies demonstrate that the sterically large tetrameric lignin model compounds undergo lignin peroxidase-catalyzed cleavage via a mechanism involving preliminary formation of an enzyme-substrate complex.
authors.affiliation: Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States. cdw@pusan.ac.kr
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Cho
authors.forename: John A
authors.initials: JA
authors.lastname: Latham
authors.forename: Hea Jung
authors.initials: HJ
authors.lastname: Park
authors.forename: Ung Chan
authors.initials: UC
authors.lastname: Yoon
authors.forename: Paul
authors.initials: P
authors.lastname: Langan
authors.forename: Debra
authors.initials: D
authors.lastname: Dunaway-Mariano
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Mariano
mesh_terms: D000873:Anthracenes / Q000737:chemistry / Q000378:metabolism*; D002244:Carbon / Q000737:chemistry / Q000378:metabolism*; D002384:Catalysis; D002412:Cations / Q000378:metabolism; D004583:Electrons; D005453:Fluorescence; D055772:Green Chemistry Technology; D006418:Heme / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D008031:Lignin / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism; D008956:Models, Chemical; D009570:Nitriles / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D055668:Photochemical Processes; D058105:Polymerization; D013237:Stereoisomerism
chemical_list: C521244:9,10-dicyanoanthracene; D000873:Anthracenes; D002412:Cations; D009570:Nitriles; D006418:Heme; D002244:Carbon; D008031:Lignin; D006861:Hydrogen Peroxide; D007501:Iron; D010544:Peroxidases; C042858:lignin peroxidase